I imagine it might've been alot like your SWAPS. But you are not obligated to send anything in particular or to meet any certain dollar value.
You make a list of little things you like to collect, hobbies, fave colors, and low cost little items that you'd like to have more of.
Your list is given to a Random Member and you receive a list from some other Random member. You send eachother atleast one package a month for like 6 months. Then at the end you get to find out who your pal was.
It was a lot of fun and so much fun to get suprises in the mail!